1. Field of the Invention
The present invention relates to motorcycle accessories. More particularly, the present invention relates to an improved construction for a fan unit or a horn and fan combination unit for a motorcycle.
2. Description of the Related Art
In a V-twin motorcycle engine, the heat from the front cylinder tends to radiate back onto the rear cylinder due to the air current during forward motion of the motorcycle. The problem of overheating the rear cylinder is particularly troublesome in slow moving traffic, where heat from the front cylinder slowly drifts rearward to heat the fins of the rear cylinder. Basically, the rear cylinder can become more heated than the front cylinder, because the front cylinder is exposed to the cool air in front of the motorcycle, whereas the rear cylinder is exposed to the heated air exiting the fins of the front cylinder. Overheating of the rear cylinder can cause the engine to cut off (due to overheating protection circuits) and can shorten the life of the motorcycle's engine.
In the background art, a so-called “parade” fan unit has been employed to reduce the overheating of the front and/or rear cylinders. A parade fan unit is basically an electrically powered fan, mounted to a bracket. The bracket is attached to the motorcycle's engine, e.g., by loosening or removing a bolt on the engine head, inserting a channel or mounting hole of the bracket about the bolt's mounting hole, and then replacing and/or tightening the bolt. Such a parade fan unit is large and highly visible. As such, a parade fan unit detracts from the appearance of the motorcycle. Also, because the parade fan unit is mounted directly to the engine, the engine's vibration may loosen the attachments of the supporting bracket such that the fan unit falls off. Also, the vibration tends to shorten the lifespan of the fan components (e.g., fan shaft bearings).
Another variety of auxiliary cooling device for a motorcycle in the background art is an electrically powered fan unit mounted to the frame of the motorcycle. The fan unit directs cooling air at the engine. Such a fan unit is described in U.S. Published Application 2010/0300791, which is incorporated herein by reference. Mounting the fan unit to the frame of the motorcycle, as opposed to the engine, reduces the vibration drawbacks of the parade fan unit described above, because the engine vibration transmitted to the frame is substantially reduced by vibration-dampening engine mounts. However, such a fan unit requires its own dedicated fan-to-frame mounting hardware and may be visible as an additional unit added to the motorcycle. Some riders prefer not to have a fan unit as an observable, additional unit on the motorcycle. Also, some riders prefer not to have an additional mounting bracket added to the motorcycle frame. A mounting hole in the frame is a permanent alteration, which can reduce the mechanical integrity of the frame and value of the motorcycle. A friction clamp mounting can damage the frame paint, and is viewed by some riders as having a cheap appearance.
Yet another variety of auxiliary cooling device for a motorcycle in the background art is an electrically powered fan unit mounted to the frame of the motorcycle at the hole previously used to mount the horn assembly. Such a fan unit obviates the need for new, dedicated fan-to-frame mounting hardware, since the hardware attaches to the horn mount provided by the original equipment manufacturer (OEM). Such a cooling device is marketed by LeNale Engineering (http://myworld.ebay.com/lenale-engineering) and depicted in FIG. 8.
As shown in FIG. 8, a front cylinder 1 and a rear cylinder 3 are disposed so as to provide a V-shaped void air space 5 therebetween. A fastener 7 (such as a bolt for engaging a nut) is passed through the mounting hole for the horn, where the mounting hole (previously used to mount the original horn unit) is formed in a downward protruding flange 9 of the motorcycle's top frame member 11. A gas tank 13 and a seat 15 may be disposed above the top frame member 11.
The fastener 7 attaches a bracket 17 to the flange 9 of the top frame member 11. The bracket 17 supports a fan unit 19. A horn 21 is positioned below the fan unit 19 and is also supported by the bracket 17. Blades 23 of the fan unit 19 are visible through a protective grill 25.
The fan 19 directs its air flow through the void air space 5 between the front and rear cylinders 1 and 3. The air flow causes a thermal break between the front cylinder 1 and the rear cylinder 3. In other words, the heated air from the front cylinder 1 is caused to exit laterally relative to the forward motion of the motorcycle. The heated air of the front cylinder 1 no longer fully impacts the cooling fins of the rear cylinder 3. Rather, cool environmental air from the lateral side of the motorcycle is drawn into the void area space 5 between the front and rear cylinders 1 and 3 and is used to supplement the cooling of the fins of the rear cylinder 3. By this arrangement, the front and rear cylinders 1 and 3 can operate at substantially the same temperature.